EventStreamer

A sample app showing how to stream data to Azure Event Hubs.

Getting Started

Run The Streamer Locally

Ensure that you have Xcode installed, otherwise this sequence of steps won't work.

• Run the PrepareXCodeProj.sh script via CLI which will prepare the build the project and create an Xcode project file.

  ./PrepareXCodeProj.sh

• When prompted to open the EventStreamer project, select Open.

• Edit the target's scheme, adding the following Environment Variables with the corresponding values:

  • SASPolicyName
  • SASPolicyKey
  • EventHubNamespace
  • EventHubPath

  If these environment variables are not set, the app will still run; it just won't stream anything to Azure.

• Run the app; you should notice events being printed in your console output:

  2019-02-22 14:29:33		depo...	1000 		["current": 1000, "name": "deposit", "initial": 1000]
  2019-02-22 14:29:33		with...	50 		["current": 50, "name": "withdrawal", "initial": 50]
  2019-02-22 14:29:33		purc...	10 		["current": 10, "name": "purchase", "initial": 10]
  2019-02-22 14:29:34		purc...	12 		["current": 12, "initial": 10, "name": "purchase", "previous": 10]
  2019-02-22 14:29:35		purc...	14 		["current": 14, "initial": 10, "name": "purchase", "previous": 12]
  2019-02-22 14:29:37		depo...	1003 		["current": 1003, "initial": 1000, "name": "deposit", "previous": 1000]
  2019-02-22 14:29:38		with...	56 		["current": 56, "initial": 50, "name": "withdrawal", "previous": 50]
  2019-02-22 14:29:38		purc...	14 		["current": 14, "initial": 10, "name": "purchase", "previous": 14]
  2019-02-22 14:29:39		purc...	14 		["current": 14, "initial": 10, "name": "purchase", "previous": 14]
  ...

  

Run The App In A Docker Container

Ensure that you have Docker installed and running, otherwise this sequence of steps won't work.

• Update the Dockerfile with the following configuration:

  FROM swift
  ENV SASPolicyName="SharedAccessKey"
  ENV SASPolicyKey="Jp9cUB1iCF="
  ENV EventHubNamespace="divergent"
  ENV EventHubPath="streamer"
  WORKDIR /temp
  COPY . ./
  CMD swift package clean
  CMD swift run

• Build the Docker image and tag it using:

  docker build --tag streamer .

Local

• Run and cleanup the image on completion. To stop the streamer, hit Ctrl + C.

  docker run --interactive --tty --rm streamer

  

Azure Container Instances

• Create an Azure Container Registry via the portal; the script assumes a registry of name `` so feel free to update the following commands with the appropriate reference.
• Run the following commands to push the container into Azure:

  registry=address.to.registry # example streamer.azurecr.io
  
  sudo docker login $registry
  sudo docker tag streamer $registry/streamer
  sudo docker push $registry/streamer

• Create an Azure Container Instance resource in Azure and provide the details for your private registry. Upon deployment, the container should automatically start executing.

How the Streamer Works

It's all about the EventStreamer.stream(to:using:until:invoking:maxWait:completion:) method. Lets see some examples.

Example A

let policy = AzureCocoaSAS.SharedAccessPolicy(name: "SharedAccessKey", key: "Jp9cUB1iCF=")
let hub = EventHub(namespace: "divergent", name: "streamer") // => http://divergent.servicebus.windows.net/streamer
let token = try? AzureCocoaSAS.token(for: hub.endpoint.absoluteString, using: policy, lifetime: 60 * 60) // expires after 1 hour

let streamer = EventStreamer(name: "myevent")
streamer.stream(to: hub, // `hub` being `nil` will result in no data being sent to Azure (i.e. offline mode)
    using: token, // `token` being `nil` will result in no data being sent to Azure (i.e. offline mode)
    until: { _ in true == false }, // only stop when this condition is met; this is a function mathing signature: (EventSequence)->Bool
    invoking: { print("\($0.current)") }, // execute this block on each event begin streamed; this is a function mathing signature: (EventSequence)->Void
    maxWait: 5, // wait, at most, 5 seconds before streaming out the next event
    completion: { print("Done streaming.") }) // execute this block when the termination condition is met; this is a function mathing signature: (Void)->Void

Expect to see something like the following in your console output:

Event(name: "myevent", value: 112)
Event(name: "myevent", value: 111)
Event(name: "myevent", value: 113)
...

Note: your initial value will differand so will the subsequent values; the sequence generator EventSequence is designed such that the next value in the sequence is based on the current value of that sequence.

Example B

let policy = AzureCocoaSAS.SharedAccessPolicy(name: "SharedAccessKey", key: "Jp9cUB1iCF=")
let hub = EventHub(namespace: "divergent", name: "streamer") // => http://divergent.servicebus.windows.net/streamer
let token = try? AzureCocoaSAS.token(for: hub.endpoint.absoluteString, using: policy, lifetime: 60 * 60) // expires after 1 hour

let sequence = EventSequence(name: "myevent", initialValue: 500)
let streamer = EventStreamer(sequence: sequence)
streamer.stream(to: hub, // `hub` being `nil` will result in no data being sent to Azure (i.e. offline mode)
    using: token, // `token` being `nil` will result in no data being sent to Azure (i.e. offline mode)
    until: { $0.current.value < 495 || $0.current.value > 505 }, // only stop when this condition is met; this is a function mathing signature: (EventSequence)->Bool
    invoking: { print("\($0.current)\t \($0.dictionary)") }, // execute this block on each event begin streamed; this is a function mathing signature: (EventSequence)->Void
    maxWait: 1, // wait, at most, 7 seconds before streaming out the next event
    completion: { print("Done streaming.") }) // execute this block when the termination condition is met; this is a function mathing signature: (Void)->Void

Expect to see something like the following in your console output:

Event(name: "myevent", value: 500)	 ["initial": 500, "name": "myevent", "current": 500]
Event(name: "myevent", value: 499)	 ["initial": 500, "name": "myevent", "current": 499, "previous": 500]
Event(name: "myevent", value: 507)	 ["initial": 500, "name": "myevent", "current": 507, "previous": 499]
Done streaming.

Note: your initial value will be 500 but subsequent values may differ; the sequence generator EventSequence is designed such that the next value in the sequence is based on the current value of that sequence.